1. Field of the Invention
The present invention relates to a multi-stage type transmission in which a plurality of speed-change hydraulic devices selectively operable in sequence depending upon various speeds are carried by an input shaft and an output shaft, and in which fluid supply lines for feeding pressure fluid from a pressure source to the clutch devices are connected between rotatable and non-rotatable parts without the use of any members which are disposed in axial alignment and in frictional contact with one another.
2. Description of the Prior Art
Generally speaking, the transmission efficiency of an automatic transmission is lower than that of a manual transmission, and the size of the external configuration of the automatic transmission is greater than that of the manual transmission required to obtain substantially the same output. Particularly, when the automatic transmission is employed in FF or RR type automobiles in which the output shaft as well as the crank shaft of the engine are arranged laterally of the vehicle, the automatic transmission is normally installed within an engine compartment of limited available space. For this reason, an increase in transmission efficiency and reduction in weight and size are very important.
In conventional multi-stage type automatic transmissions, the axial length of the transmission had to be extended and greater external size thereof had to be used for the convenience of arrangement of the speed change gearing or clutches within the casing, and therefore, particular consideration had to be given to the employment thereof. In order to actuate various clutch devices disposed within the casing of the multi-stage type automatic transmission, fluids for actuating the clutches must be fed through a connection in a flow passage between a rotatable part of the side of the rotating shaft and a non-rotatable part on the side of the casing. In the conventional multi-stage automatic transmissions, however, at least two seal rings are required for each flow passage in the connection between the rotatable part and non-rotatable part which calls for additional axial length on opposite sides of the seal rings for mounting thereof, and the need for a minimal clearance between the rotatable part and the non-rotatable part to allow relative rotation therebetween. Additionally, the axial length of the multi-stage automatic transmission had to be further increased.
Furthermore, in the conventional multi-stage automatic transmissions, the axial force exerted on each seal ring when the working fluid is fed to each clutch device produces frictional contact between the rotatable part and the non-rotatable part, resulting in a loss of power. This loss of power results in a significant decrease in transmission efficiency. Also, the seal ring is cut at one place thereof for the convenience of its mounting into a mounting groove. However, leakage of fluid in the cut section occurs to an extent which is not negligible, and hence the fluid pump must be increased in capacity in order to compensate for the leakage of the fluid, unavoidably resulting in the decrease in efficiency of the multi-stage automatic transmission and increase in size and weight thereof.